This invention describes an armature for induction heating of a food container such as a plate or dish, saucepan, bowl, glass or bottle.
The armature is located in, on or under the bottom of said container.
The armature is deposited, engraved, cut out and then glued, integrated, machined, or stamped, on, under or in the bottom of the container. The armature can also be part of the structure of the container (saucepan or specific pastry boat). It can also be chemically, physically, mechanically or thermally treated in a selective manner.
More specifically, the invention describes an armature intended for heating in the presence of a specific inductor, having characteristics which improve user safety, protection of the inductor from power surges, and electromagnetic compatibility (so-called EMC) of heating. Certain aspects of the specific inductor contribute to the invention.
Zones of potential application for induction heating and cooking are especially sensitive to EMC, in particular hospitals, which have a great deal of electronic instrumentation, aircraft, nursing homes, trains and boats. Absolute respect for the EMC restriction is the condition for development of inductive heating in these markets.
Induction-heated plates are described in Patent Application FR 9614475 and Utility Model Application FR 9706059 by the same inventor, and inductor examples are also described. This invention can be adapted to inductors and armatures described in these documents, and reference will be made in the description to inductor and armature diagrams.
Protection of the inductor, which is located in a base of the container, such as a tray, place mats, or an induction plate, requires that the container having an armature have an impedance that conforms to the standard.
If an armature is too conductive, it risks short-circuiting the inductor and producing a power surge of heat detrimental to its service life.
An armature which is too resistant will produce too little heat.
The heating power is controlled by the user, with effective powers varying within a wide range. It is therefore important that measurement of instantaneous power not be the only factor taken into account by the inductor in triggering its safe mode.
Protection of the consumer means that the inductor cannot induce current anywhere other than the containers intended for this purpose. This also contributes to preservation of the power source of the induction system, and the inductor tray or placements can be used without fear that the presence of a metallic ground will trigger induction.
Thus, the inductor does not react to the presence of place settings, saucepans, bracelets, watches, and other things, such as mobile phones.
Electromagnetic compatibility requires that the inductor not emit into the environment an electromagnetic field capable of disturbing any electronic devices.
Electromagnetic compatibility is optimized by the following inductor characteristics:
Confinement of the magnetic field, low frequency of the electromagnetic field, low rate of harmonics, actuation of induction exclusively in the presence of the armature absorbing the radiation, strong coupling between the armature and the inductor.
According to the invention, the inductor is a flat circuit comprising two coils 1 and 2 as shown by the embodiment in FIG. 1.
We would like to point out the opposite directions of the coils, and magnetic field B which crosses the two coils.